Display system

ABSTRACT

A panoramic display system for use in a vehicle equipped with a plurality of episcopes (22) includes an information gathering sensor and a plurality of displays (24) for the gathered information. Each display (24) is associated with a respective episcope (22) and is operable to display the information gathered from a field of view corresponding to the respective episcope.

This invention relates to a display system, and in particular but notexclusively to a panoramic display system.

There is a common requirement in military vehicles for panoramic vision,to assist the vehicle crew in surveillance and target acquisition,situational awareness and vehicle control. In daylight conditions thismay be provided by windows. To reduce the vulnerability of the vehicledue to penetration of the windows by shrapnel or small-arms fire it iscommon to provide the windows with "episcopes" which comprise glassrhomboid blocks which act as unity-magnification periscopes. Theepiscopes may be arranged in a ring with their viewing apertures alignedto provide a panoramic field of view. During night operation, or in thepresence of smoke or intense light sources, the utility of theseepiscopes is limited and their use may even present a hazard. It is thusnecessary to provide some other form of panoramic sensor, such as athermal imaging system. Advances in such sensors now allow informationto be gathered over 360° with resolution comparable to that of the eye,but there is considerable difficulty in displaying such information inan easily assimilated form within the confines of a typical armouredfighting vehicle (AFV). Displays of moderate size have inadequateresolution to provide a panoramic display, such that an operator willtypically have to select a limited field of view for display on a singlerelatively small screen. In this situation it is generally not possibleto locate the position of a threat within the 360° arc with the samerapidity as is possible with the direct-view episcopes.

It is among the objects of the embodiments of the present invention toprovide a indirect viewing system which obviates and mitigates thesedisadvantages.

According to the present invention there is provided a panoramic displaysystem for use in a vehicle equipped with a plurality of episcopes,including an information gathering sensor and a plurality of displaysfor the gathered information, each display being associated with arespective episcope and being operable to display the informationgathered from a field of view corresponding to the respective episcope.

In use, the operator may utilise the episcopes in the normal mannerwhile conditions permit. However, in poor visibility the sensor anddisplays may be utilised to provide indirect viewing of the same or asimilar scene. Operators will thus only require minimal retraining toacquire an indirect viewing capability comparable with the existingdirect view capability, as the display will closely mimic the viewsobtained from the episcopes.

As used herein, the term episcopes is intended to encompass conventionalepiscopes as described above, as well as periscopes and other directviewing arrangements in which a reflected or redirected image is viewed.

Preferably, the gathered information is provided with substantially unitmagnification, to correspond with the unit magnification provided by atypical episcope. The facility to increase magnification selectively maybe provided to permit an operator to zoom in on a particular scene.

The indirect displays may be viewed in conjunction with the respectiveepiscopes, or may be arranged for exclusive viewing. The indirectdisplay may be provided adjacent the episcope aperture, or may beoverlaid on the directly viewed scene. Conveniently, the latterarrangement is achieved by injecting the indirectly viewed scene intothe visual path of the respective episcope such that it appears at theepiscope aperture.

Preferably also, each display is collimated, to allow relaxed viewing.The display and associated collimator may be separate from the episcope,but savings in space may be achieved by integrating one or both of thecollimator and display with the episcope. The collimating optics mayintroduce residual distortions which may be compensated by distortingthe electronic image sent to the display.

The displays may be moveable to cover the episcope apertures, or theepiscopes may be provided with shutters or spectral filters, such thatstray light from the vehicle interior or the indirect display is notvisible outside the vehicle through the episcopes.

One or more information gathering sensors may be provided and may be inthe form of one or more of, for example, thermal imaging sensors, radar,or low light TV.

The displays may be electronic displays in the form of a transmissiveliquid crystal or electro-chromic device with an illuminating lightsource, or may be self-luminous, such as a CRT or electro-luminescentdisplay.

This and other aspects of the present invention will now be described,by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a somewhat schematic representation of part of an armouredfighting vehicle (AFV) provided with a series of episcopes, to providepanoramic vision, in accordance with the prior art;

FIG. 2 is a similar view to FIG. 1, in which the episcopes are providedwith indirect displays, in accordance with a first embodiment of thepresent invention;

FIGS. 3a and 3b are somewhat schematic views of an episcope for use inan AFV, in which an indirect display is collimated and injected into thevision path of the episcope;

FIG. 4 is a somewhat schematic view of an episcope in which the indirectdisplay is injected into the visual part of the episcope and thecollimator is integrated with the episcope; and

FIGS. 5a, 5b and 5c are somewhat schematic views of further alternativearrangements for injecting an indirect image into an episcope.

Reference is first made to FIG. 1 of the drawings, which is a somewhatschematic illustration of a tank turret 10. In order to provide theoperator 12 with a panoramic view, a series of windows are providedaround the circumference of the turret 10, and to reduce thevulnerability of the vehicle due to penetration of the windows byshrapnel or small arms fire each window is provided with an episcope 14comprising a glass rhomboid block which acts as a unity magnificationperiscope. Such rhomboid blocks are frequently split to give an internalair gap to prevent transmission of mechanical shock, but this refinementis not illustrated in the figure. In normal daylight conditions, theepiscopes 14 provide the operator 12 with a 360° direct view capability.The displays are integrated with cueing devices to assist in alertingthe vehicle crew to an arc in which a possible threat has been detected.However, in restricted visibility, the operator 12 must rely uponindirect viewing systems utilising, for example, one or more of thermalimaging sensors, radar or low light TV. Conventionally, the indirectimages obtained from these sensors, which may gather information over a360° field of view, is displayed on a single screen, the operatordetermining the particular field of view to be displayed on the screen.Accordingly, it is difficult for the operator to locate the position ofa threat within the 360° arc with the same rapidity as is possible usingthe direct view episcopes 14.

Reference is now made to FIG. 2 of the drawings, which illustrates atank turret 20 equipped with a display system in accordance with a firstembodiment of the present invention. In a similar manner to theconventional turret 10 described above, a plurality of episcopes 22 areprovided in a ring to provide the operator 12 with a panoramic directview capability. However, additional flat panel LCD displays 24 aremounted on the inner faces of the episcopes 24. The displays 24 arelinked to a thermal imaging sensor 26 which gathers information over360°. The image appearing on each display 24 corresponds to the directview obtained from the aperture 28 of the respective episcope 22 onwhich the display is mounted. For direct compatibility with the directview screen, the indirect image is displayed with substantially unitmagnification. Also provided is a single, large monitor 29 (shown behindthe operator), central and convenient to the operator; the detail shownon the panoramic indirect displays may be insufficient to permit propertarget identification recognition and weapon cueing. The smallerindirect displays 24 thus incorporate a control, operated by theoperator by touch or other means, to display selected information fromone of the smaller displays on the central monitor 29.

In darkness, it is frequently important that stray light from theinterior of the vehicle should not be visible from outside the ring ofepiscopes 22. This may be ensured by arranging the displays 24 such thatthey may cover the episcope apertures 24 when the episcopes 22 are notin use.

Reference is now made to FIG. 3a of the drawings, which illustrates asingle episcope 32 in which the indirectly viewed screen is injectedinto the visual path of the episcope such that the image appears at theepiscope aperture 34. In this example, the display 36 is in the form ofa transmissive liquid crystal with an illuminating light source in theform of a lamp 38. A diffuser 40 is provided between the lamp 38 and thedisplay 36, and the projected image from the display 36 is passedthrough a collimator 42, to allow relaxed viewing.

The display 36 is provided above the upper end of the episcope 32, whichin this arrangement is provided with a plane upper face 44 defined by aprism 45. The episcope 32 is provided with a 45° beam splitter 46 forreflecting the direct view image. Both the direct and indirect imagesare reflected from the lower rhomboid episcope face 48 and are visibleat the episcope aperture 34.

FIG. 3b of the drawings illustrate an arrangement in which a lamp 52,diffuser 54, display 56, and collimator 58 are provided towards thelower end of an episcope 60, directly behind the aperture 62.Accordingly, the lower portion of the episcope is provided with a planerear face 64 defined by a prism 65, and the beam splitter 66 is providedto reflect the incoming direct image.

Rather than providing a separate collimator as illustrated in theembodiments of FIGS. 3a and 3b, it is possible to integrate thecollimator with the episcope, as illustrated in FIG. 4 of the drawings.In this embodiment a lamp 70 (or spectrally narrow source such as avisible laser LED), diffuser 72, LCD display 74 and narrow band filter76 are provided below the lower end of the episcope 78. The lowerrhomboid episcope face 80 is plane, defined by a prism 81, and theindirect image is transmitted through a beam splitting coating 82 on thelower rhomboid episcope surface 84, which coating is partiallytransmissive, partially reflective in the spectral region of the display74, and is reflective over the remainder of the visual wave band. Theupper end of the episcope 78 is provided with a 45° prism 86 providedwith a concave reflecting surface 88. The upper rhomboid episcopesurface 90 is provided with a beam splitter 92 which is transmissive inthe spectral region of the display and reflective over the remainder ofthe visual wave band. In the illustrated embodiment the beam splittingcoating 82 is polarising, and in this situation the concave reflectingsurface 88 is provided on a quarter wave plate 94. If the beam splittingcoating 82 is not polarising the prism 86 and plate 94 may be providedas a single component. The brightness of the displayed image and theview of the outside world can both be maximised by using a narrow bandlight source (laser, LED or narrowband CRT phosphor) and holographicelements to act as the various beamsplitters and collimating mirrors.

To prevent stray light being visible from outside the vehicle, theportion of the episcope 78 which is visible from exterior of the vehicleis provided with a spectral blocking filter 96.

In further embodiments of the present invention, it is possible to formthe collimator using a holographic optical element, and embodimentsincorporating this feature are illustrated in FIGS. 5a, b and c of theaccompanying drawings. Reference is first made to FIG. 5a, whichillustrates a lamp narrowband light source 100 such as a laser ormonochromatic LED, diffuser 102 and display 104. The image from thedisplay 104 is reflected from the lower rhomboid surface 106 of theepiscope 108 and then reflected by a collimating powered non conformalhologram 110 provided towards the upper end of the episcope 108 andextending normal to the main rhomboid axis. The collimated images arethen reflected from the lower rhomboid surface 106 and projected throughthe episcope aperture 112.

FIGS. 5b and 5c illustrate other configurations in which the lamp 100,diffuser 102 and display 104 are in different positions relative to theepiscope 108 and in which the hologram 110 is differently oriented (FIG.5c). It is also possible to form the holographic optical element on oneof the existing plane surfaces of the episcope.

It will be clear to those of skill in the art that the above-describedembodiments are merely exemplary of the many system configurationspossible within the scope of the present invention. It will also beevident to those of skill in the art that the above-describedembodiments may be subjected to modifications and improvements, withinthe scope of the present invention.

We claim:
 1. A panoramic display system for use in a vehicle equippedwith a plurality of episcopes, the system including an informationgathering sensor for gathering information and a plurality of displaysfor gathered information, each display for association with a respectiveepiscope and being operable to display information gathered from a fieldof view corresponding to the respective episcope, further including alarger central display device for displaying selected information fromone of said plurality of displays.
 2. The system of claim 1, wherein theplurality of displays display information with substantially unitmagnification.
 3. The system of claim 1, wherein each display isprovided with one of a shutter and a spectral filter to prevent emissionof stray light through an associated episcope.
 4. The system of claim 1,wherein each display is collimated, to allow relaxed viewing.
 5. Thesystem of claim 1, wherein each episcope defines a visual path and eachdisplay is arranged to inject an image therefrom into the respectiveepiscope visual path.
 6. The system of claim 1, wherein each display isprovided adjacent a respective episcope aperture and is movable to coverthe aperture when a respective episcope is not in use to preventemission of stray light through the episcope.
 7. The system of claim 1,wherein each display is a transmissive liquid crystal with anilluminating light source.
 8. The system of claim 1, wherein eachdisplay is an electro-chromic device with an illuminating light source.9. The display of claim 1, wherein each display is self-luminous. 10.The display of claim 1, wherein each display includes a collimator inthe form of a holographic optical element.
 11. The display of claim 10,in combination with a plurality of episcopes wherein each saidholographic element is formed on a plane surface of a respectiveepiscope.
 12. The system of claim 1, in combination with a plurality ofepiscopes.
 13. A panoramic display system for use in a vehicle equippedwith a plurality of episcopes, the system including an informationgathering sensor and a plurality of displays for gathered information,each display for association with a respective episcope and beingoperable to display information gathered from a field of viewcorresponding to a respective episcope, and a central display device fordisplaying selected and magnified information from one of said pluralityof displays.
 14. A panoramic display system for use in a vehicleequipped with a plurality of episcopes, the system including aninformation gathering sensor for gathering information and a pluralityof displays for gathered information, each display for association witha respective episcope and being operable to display information gatheredfrom a field of view corresponding to the respective episcope, whereineach episcope defines a visual path and each display is arranged toinject an image therefrom into the respective episcope visual path, incombination with a plurality of episcopes wherein each display output issubstantially collimated and is injected into a respective episcopevisual path by a beam splitter at an upper rhomboid face of a respectiveepiscope.
 15. A panoramic display system in combination with a pluralityof episcopes each defining a visual path, the system for use in avehicle and including an information gathering sensor for gatheringinformation and a plurality of displays for gathered information, eachdisplay for association with a respective episcope and being operable todisplay information gathered from a field of view corresponding to therespective episcope by injecting an image from the display into therespective episcope visual path wherein each display emits within adefined spectral region narrower than the visual spectrum and eachdisplay includes a collimator comprising a concave surface on a 45degrees prism separated from an upper rhomboid surface of a respectiveepiscope by a beam-splitter which is transmissive in the spectral regionof the display and reflective over the remainder of the visual waveband,the display being injected through a lower rhomboid surface of theepiscope by a beam-splitting coating which is partially transmissive,partially reflective in the spectral region of the display and isreflective over the remainder of the visual waveband.
 16. The system ofclaim 15, wherein the beam-splitting coating of the lower rhomboidsurface of each episcope is substantially polarizing in the spectralregion of the respective display and a quarter-wave plate is insertedbetween the upper rhomboid surface and the concave colligating surfaceso that radiation which passes through said coating from the display isreflected at said coating after reflection of the colligating surface.17. A panoramic display system for use in a vehicle equipped with aplurality of episcopes, the system including an information gatheringsensor for gathering information and a plurality of displays forgathered information, each display for association with a respectiveepiscope and being operable to display information gathered from a fieldof view corresponding to the respective episcope wherein each displayincludes collimating optics and means are provided for compensatingresidual distortions of said optics by distorting an electronic imagesent to each display.
 18. A panoramic display system for use in avehicle, the system comprising a plurality of episcopes, an informationgathering sensor for gathering information and a plurality of displaysfor gathered information, each display being associated with arespective episcope and being operable to display information gatheredfrom a field of view corresponding to the respective episcope, furtherincluding a larger central display device for displaying selectedinformation from one of said plurality of displays.
 19. A panoramicdisplay system for use in a vehicle, the system comprising a pluralityof episcopes, an information gathering sensor, a plurality of displaysfor gathered information, each display being associated with arespective episcope and being operable to display information gatheredfrom a field of view corresponding to the respective episcope, and acentral display device for displaying selected and magnified informationfrom one of said plurality of displays.